Get'n to know my Compression Plugin
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Posted on Aug 06, 2009 09:47 am
Hippie
Rockstar Vatican Assassin
Member Since: Mar 20, 2009
I'm having some difficulty, for whatever reason, trying to grasp compression. Either I'm way left of field or just over-thinking this. Here's the dilly...
I currently have my bass drum configured like this:
RMS: 0
Attack: 10ms
Release: 200ms
Threshold: -22
Ratio: x:6
Knee: 8 (medium)
Makeup Gain: 6db
With the makeup gain active, I'm still getting spikes up to +9 db. My understanding of compression was that anything over 6db (my ratio) would increase the output by only 1 db. So, if normal playback is riding between -22db (threshold) and -16 db, the compressor wouldn't kick in... BUT anything above -16 would output just -15 db. So how am I seeing +9 db bursts in the mixer's signal meter?
In relation to all of this... is it possible that what I'm seeing not really happening? Since the compressor plugin is attached to the "input," the signal strength on the mixer strip is deceiving? In other words, while I'm seeing +9 redlines, the output is really okay and compressed?
Lastly... how is setting the compressor to something like 15:1 a limiter and/or squisher? I mean... if my threshold is -22 with no compression till -7, there can't be a whole lot to squish... right? Seems like there's a huge gap to work with before compression is even a factor.
Sorry for the long post..... but thanks in advance for any advice/input.
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Aug 06, 2009 06:09 pm the spikes are the initial transients that are passing through (attack time) before it actually starts compressing....try lowerin' it some and see if that helps
most compressors will allow you to view both the pre compressed levels (pre) and the actual output of the compressor (post)...try right clicknin' the meters.
and yes 15:1 with a fast attack time is limiting...it doesn't necessarily need to be "working" all the time, all it's dooin' is putting a brick wall for maximum output...so the only time it's squishing, is when yer at the level of that wall (threshold) anything under it will be unaffected.
i wrote a pretty cool article here somewhere that goes into how to set your compressor...lemme see if i can find it.
here ya go
www.homerecordingconnecti...ory&id=1470
cruxTypo SzarMember
Since: Jul 04, 2002
Aug 07, 2009 05:44 am Yeah, 10 MS on a compressor is plenty of time for a transient to make it through an cause a peak like WYD said try pulling ur attack setting all the way to the fastest setting and see if the peak disappears
in terms of happening or not, wat plugin r u using? different comps act vastly differently, especially plugin ones as most r based on different real world models. I use the Kjauerhaus Classic Compressor alot and it is not good for cutting peaks as their vintage style design doesnt really allow it to react fast or aggressively enough to do that. Its still working, but just not in that application.
elaborating a bit on WYD, 15:1 would be a limiter, but it doesnt mean it will be limiting (working as WYD) all the time. 15:1 is a limiter setting because ull almost never see a signal with enough juice to push out that 1 db vs. 15db cut, not at normal threshold levels at least. With that in mind, almost everything that happens in ur signal will get knocked back by the compressor. Its not a total limiter coz in the case of a signal that does have the juice to break through, ofcoures that will happen. A true limiter is inifinite, thus that will never happen.
HippieRockstar Vatican AssassinMember
Since: Mar 20, 2009
Aug 07, 2009 08:24 am @ WYD:
Haha... well now I know who wrote the "eHow" article!!! I found that last night in my quest for Compression knowledge. Great article BTW. If anything, I learned that I was starting backwards with the ratio and threshold. You're examples shed a bit of light on the subject and reversed my logic.
@ Crux
I'm actually using "Steve Harris Plugins" for Ardour GTK2 (Linux). The plugin by name is called "SC4 Mono." These aren't fancy by any means, but do have input/output meters to watch.
@ Both...
if the raw input signal is toggling between -24 to -18 dbs, would the threshold theoretically be -20/-21 or something lower? It just seems natural to put the threshold somewhere in-between the lows and highs, but if you set the threshold near the bottom, you risk less chance of drastic highs.
Like, here's my thinking and tell me where I'm wrong. As is with the example above, I know I have a +6 difference between -24 and -18. If I set the threshold to -21 with a ratio of 6:1, it is possible the compressor will never turn on. In order to meet the ratio, the signal would have to exceed -15db and I already know my highs only reach about -18db. So theoretically, I should set the threshold at -26 with a 6:1 ratio so that the compressor kicks on at -20dbs and leaves me with my highest points only reaching -21/-22 dbs max. In this example, I can assume all signals @ -19 and -18 is all that's getting compressed. Is this correct theory?
Or... does everything beyond the threshold actually get compressed and only gets 1db of extra output when the ratio is met? I guess where I'm getting lost is understanding when compression actually kicks in: At the Threshold or when the ratio is met? So in the case of a -26 threshold with a 6:1 ratio; is compression applied at -25db or -20dbs?
TadpuiI am not a crook's headMember
Since: Mar 14, 2003
Aug 07, 2009 10:25 am Honestly, I don't look at numbers when I'm setting my compression parameters.
If I'm wanting to tame some transients, I turn the threshold down until I see that the compressor is engaging only intermittently (mine has a red LED that turns on any time the comp is engaged). How often it engaged is a sign of how light or heavy the compression is according to the threshold setting. So if I want to make something's dynamic range much more narrow, I set the threshold to where the LED is really blinking most of the time. Or if I really want to squish the hell out of something, I set it to where the LED is only off intermittently.
Then I use my ears to set the ratio, attack, and release.
I like the suggestion of using drastic threshold and ratio settings to help you hone in on attack and release settings, it does really help you hear what you're doing. It really emphasises what the compressor is doing. Then turn them back down to normal levels after you've set the attack and ratio.
But I leave the numbers out of it for the most part. I couldn't tell you what actual number I use for anything except maybe attack and release. But even then, I let the instrument I'm tracking/editing be the guiding force in my compression settings.
That's not to discount the importance of understanding compression and all of its parameters. And I think you're asking good questions here. To do my best to answer your last question, the compressor engages only when the threshold is exceeded. So when your signal exceeds -26 dB in this case, the compressor will engage.
The ratio does not affect when the compressor engages, it only affects how much attenuation the compressor applies to your signal once it does exceed the threshold.
So with a 6:1 ratio:
if your signal exceeds your -26 dB threshold by 6 dB, the compressor will attenuate down to only 1 dB over the threshold (+6 dB in, +1 dB out...there's your 6:1 ratio).
- if your signal hits -20 dB (your threshold +6 dB), it'll leave the compressor at -25 dB (your threshold +1 dB).
- If your signal hits -14 dB (your threshold +12 dB), it'll leave the compressor at -24 dB (your threshold + 2 dB).
- if your signal hits -8 dB (your threshold + 18 dB), it'll leave the compressor at -23 dB (your threshold +3 dB).
So you can start to see that a 6:1 ratio is a pretty heavy compression setting. It really flattens out the signal strength once it exceeds your threshold. I'd reserve that for when you want a kick or snare drum to really slam, or when you're trying to get a dry bass guitar to hum along with a consistent level.
Generally, a 3:1 ratio is plenty to tame transients on vocals, acoustic instruments, and drum overheads. I generally don't use anything higher than 5:1 when working with percussion, although i do love to put a limiter (not a brick wall limiter, but one with a somewhat gentle attack) on a kick and snare to really make them hit hard and loud.
Wikipedia has a great article about dynamic compression:
en.wikipedia.org/wiki/Dynamic_range_compression
HippieRockstar Vatican AssassinMember
Since: Mar 20, 2009
Aug 07, 2009 12:01 pm D@#n....... I love this forum. You guys are seriously awesome with your explanations. Here's a pic of my plugin; As you can see, not very "gui" but very flexible (down to the 100ths/1000ths for any setting).
I did forget to mention I was working with kick-drum; that explains why I was working with 5-8 ratios. The kick in my mix is way to dynamic in volume. It goes from -23 to like -10. I guess that's why I was looking for a mathematical take on how to hone in on the correct compression. What you guys have all provided helps to clarify where I need to go. THANKS!!!!
cruxTypo SzarMember
Since: Jul 04, 2002
Aug 07, 2009 10:56 pm I'm comin back to this coz it literally took me years to feel comfortable using a compressor, so I FEEL U
U got alot of numbers going on there, and im not particularly a numbers guy so like tadpui said, maybe its time to go to ur ears.
When figuring out compression, if u have a Gain Reduction Meter as i see u do, u can usually just set ur Ratio to something standard like 3-5:1 and keep pushing down ur threshold until u get about 3 or 6 db of GR. Ive found that 3 to 6 is usually acceptable and isnt really squishy. If ur using 3:1 and ur getting the 3-6 db off, and u still dont "hear" the control u want then definitely kick up ur ratio until u feel like the peak ur aiming for is not so harsh. Ofcourse ur attack and release will factor in to this, a very easy way to set them is just to start off with ur release about halfway, lets say 20-40 MS and ur attack as fast as possible. To "hear" the attack, just keep rolling it back until u hear the "clicking" of ur instrument since that should be wat was killed when it was attacking almost instantly. When u get a good thick clicking ur happy with u can move ur release until it compliments that click with some body. doing this with a kick drum should help it be obvious to ur ears as the kick has an attack and a bit of a ring.
side note... if ur kick drum is very dynamic but not necessarily peaking so much its ruining ur track maybe setup ur really hardcore compression on a bus and do it in parallel. y waste good dynamics right?
Aug 07, 2009 11:34 pm LOL somebody actually read that on eHow! lol yeah i threw it up there a while back, cuz well it's the only cool thing like that i've written....haha glad to see someone read it on there.
